Promise is not always everything it's cracked up to be. Playwright Rajiv Joseph, whose plays frequently explore the intersection between bloody human violence and supple human relationships, has injected plenty of it into his play The North Pool, which just opened at the Vineyard Theatre. But the more layers he peels away over the course of this reserved two-hander, the less we learn and care about the characters who are supposed to command our attention.

Joseph is perhaps best known for his Pulitzer Prize finalist Bengal Tiger at the Baghdad Zoo, but has spent much of the last decade composing a catalog of works chronicling young people's fights against the world, their families, and themselves. So when, at the start of this evening, which has been directed by Giovanna Sardelli, he ushers us into the vice principal's office at a crowded high school in the late afternoon on the last day of classes before Spring Break, the thing we're most anticipating is fireworks.

For a while, it seems like we're certain to get them. Dr. Danielson (Stephen Barker Turner) has summoned a student, Khadim (Babak Tafti), to see him before leaving for the week — and it's not immediately clear why. Khadim isn't getting poor grades (he has a B average), and he's not proven himself a troublemaker in the months since his transfer. There's just the hint of a problem: Khadim's apparently having gone home after a recent fire drill that occurred during the final period of the day. But surely that's not a punishable offense?

Perhaps not. But as Danielson lays and springs an increasingly complex series of traps, holes begin developing in Khadim's story about both that day and his life. Was he even in class that day at all? If not, where was he? What has he been doing in the basement, where only his locker (out of some 3,000 in the school) is located? Why have his parents been out of the country, in Saudia Arabia, for a month, and what is he doing alone at home while they're gone? Why was he kicked out of an elite private academy? And what connection, if any, did he have with a "troubled girl" named Lia Winston, who committed suicide earlier in the term?

All of these questions are, of course, interconnected, and by the end of the 90-minute play, we've learned exactly who Khadim is and why he's not just a threat to Danielson, but more like the middle-aged man than either might like to admit. Joseph does not have any particular trouble navigating the intricate plot and its myriad deceptions, which at various points involve everything from parrots to cell phones to PVC piping to an underground bomb shelter located on campus (the slang term for which serves as the work's title).

But if Joseph has provided an intriguing basic foundation, his attempts to build it out are usually half-hearted and even more frequently boring. None of the answers to the mysteries surrounding Khadim are explosive, and at their best most of them are contrived and casual. Worse, the stakes for both men are shockingly low. It takes us far too long to discover what drives either man, and the tension between them crackles so little that even when they discover what they have in common, your reaction is less likely to be "ah ha" than "about time."

The nervously driving nature of Dr. Danielson and the brusque, aloof attitude Khadim demonstrates in return don't leave much room for good performances. Even so, Turner is shrill in presenting Danielson's quest for the truth, and never varies either his vocal cadences (medium bitter) or his emotional intensity (marginal) as circumstances ought to dictate. Tafti is slightly better, but he lets Khadim remain so soulless for so long that when he eventually warms up, you can't completely accept the transformation.

Though Donyale Werle's office set is just as cramped and institutional as it should be, Sardelli doesn't make much use of it, and her staging is inert and less than inventive throughout. Not that she's been given many opportunities. Despite having a few genuine points to make about prejudice and secrecy in war time, and gently portraying this event as a caution-inspiring microcosm of the recent Iraq war, Rajiv hasn't given her the freedom she needs. As with his characters here, he's boxed her in by trying to pretend we're watching two fearsome beasts when they're able to summon up few feelings stronger than indifference.

The North PoolThrough March 24
Vineyard Theatre, 108 East 15 Street
Tickets online and current Performance Schedule: Vineyard Theatre